The invention relates to an ultrasonic image processing method for displaying an ultrasonic examination image sequence of an artery segment with indications of the arterial dilation in function of the cardiac cycle. The invention also relates to an ultrasonic examination imaging system for carrying out this method.
The invention is used in the field of ultrasonic diagnostic imaging, for providing cardio-vascular non-invasive diagnostic tools for studying anomalies of arteries and notably stenoses. A primary diagnostic criterion for a stenosis is an abrupt reduction of the diameter of a suspect artery segment observed in an artery image. A more elaborate criterion is the study of the artery diameter dilation in function of the instant of the cardiac cycle and in function of the location along the artery segment. Therefore, in order to early diagnosing stenosed arteries, the medical field has a need for non-invasive means for providing artery images together with clear quantified indications of the arterial dilation. As a matter of fact, it is important to use non-invasive means instead of invasive means because invasive means modifies the artery pressure, hence the actual arterial dilation.
An ultrasonic image processing method for calculating dilation curves related to an artery segment is already known from the U.S. Pat. No. 5,579,771 (Bonnefous, Dec. 3, 1996). This document describes a method for characterizing an artery segment by ultrasonic imaging, using an array of ultrasonic transducers that produces a sectional frame, which is formed by image lines of a number of successive parallel excitation lines extending perpendicularly to the artery axis. Said array is coupled to a transmitter/receiver circuit, which provides high frequency signals to a signal processing system. Said system determines the arterial walls radial velocity and displacement amplitude values and further determines an arterial dilation curve in function of location and time. Such a curve is constructed by points representing the arterial dilation value in the arterial radial direction Z, at a given location corresponding to an excitation lines along the longitudinal X-axis of the artery, in function of excitation instants t, during a cardiac cycle. So, FIG. 4C of this document shows, superposed, the different dilation curves related to all the excitation lines of an ultrasonic signal corresponding to the examined artery segment, said lines being at regularly spaced locations along the X-axis of the artery.
A problem is that these dilation curves are not readily exploitable by a cardiologist. In particular, it is difficult to actually connect a dilation curve to a given excitation line in the image provided by the set of high frequency signals related to the artery segment: that means that it is difficult to connect a dilation curve to a location in the artery segment. So, it is quite difficult to connect a dilation value and a time instant of the cardiac cycle to said location in the artery segment. Such a connection must however be established in order to perform a successful study and a precise diagnosis of the suspect zone of artery.
It is an aim of the invention to provide an ultrasonic image processing method to automatically establish such a connection.
This problem is solved by means of a method as claimed in Claim 1.
This method offers the advantage that the arterial wall behavior is made clearly visible together with the parameters that are useful to establish the diagnosis.
An ultrasonic diagnostic system having display means and means for carrying out the method is claimed in Claim 7. This system constitutes a tool for non-invasive diagnostic of arterial wall anomalies.